The present invention relates to a dry, stable bleaching composition comprising a peroxyacid compound and a compound which releases water by means of chemical decomposition.
Peroxygen bleaching agents in general and peroxyacid compounds in particular have long been recognized as effective bleaching agents for use when the adverse color and fabric damage effects of harsh active halogen bleaching agents cannot be tolerated. See, for example, Canadian Patent No. 635,620, Jan. 30, 1962, to McCune. However, utilization of these materials poses several problems. One of the problems is that organic peroxyacids decompose spontaneously releasing heat. At a certain temperature, called the self-accelerating decomposition temperature, a runaway reaction can occur which could lead to the generation of sufficiently high temperature to ignite the organic peroxyacid. This decomposition can be initiated by both point sources of heat, such as friction, or the entire sample could reach the decomposition temperature during storage or shipping.
There have been many ways suggested for controlling the exothermic reaction of peroxyacid compounds. The most prevalant method has involved the addition of a preferably neutral or slightly acidic inorganic salt hydrate to the peroxy compounds. The hydrated salts were selected to that some of the waters of hydration would be released at a temperature slightly below the decomposition temperature of the acid. Hydrated materials used include magnesium sulfate, calcium sodium sulfate, magnesium nitrate, potassium aluminum sulfate and aluminum sulfate. These and many others are disclosed in U.S. Pat. No. 3,770,816, Nov. 6, 1973, to Nielsen.
While the above-mentioned hydrated materials are able to supply water to quench the exothermic reaction, they suffer from several defects. These include the following:
1. The hydrated salts maintain sufficient vapor pressure of water in the presence of the diperoxyacid to increase the loss of available oxygen. PA0 2. The loss of water to the surroundings due to high vapor pressure reduces the amount of exotherm control. PA0 3. Many of the hydrated salts contain high levels of metal ions which increase the loss of available oxygen, reduce the shelf life of the final product and injure the cleaning performance of compositions containing the diperoxyacids.
These defects cause the formulator of dry peroxyacid products several problems and a better exotherm control mechanism is desirable.
It has been found in the present invention that a better exotherm control measure is obtained by adding a material which will chemically decompose to release water to the environment in which the peroxyacid exists. These agents not only supply all of the benefits of hydrated salts but additionally overcome the aforementioned problems.
Accordingly, it is an object of the present invention to provide a composition containing a peroxyacid compound having improved exothermic control.
This and other objects will become apparent from the description which follows.
As used herein, all percentages and ratios are by weight unless otherwise specified.